Known optical sensor elements used in an optical sample analyzing apparatus are described in WO 2010/059176 A1. This document discloses a nephelometric turbidity meter as an example for an optical sample analyzing apparatus. Another nephelometric turbidity meter as an example for an optical sample analyzing apparatus is shown in U.S. Pat. No. 5,446,544.
Known optical sensor elements can include an optical window to provide the optical interface to the sample to be analyzed. Samples to be analyzed may be liquids or gases. In known optical sample analyzing apparatuses, the sample to be analyzed is a liquid, the analyzing method is nephelometric turbidity measurement.
One of the challenges when applying an optical sensor element in an optical analyzer apparatus is moisture build-up and fogging on the inside surface of the optical sensor element due to differences in fluid temperature outside the optical window from internal air temperature on the interior side of the optical window.
In WO 2010/059176 A1 the problem of moisture buildup and fogging is addressed by applying a multiple, sealed window construction for the optical window. This, however, is complicated and expensive from a manufacturing point of view and is not service-friendly. For example, in instances when fogging still occurs, the whole optical sensor element has to be exchanged.
In U.S. Pat. No. 5,446,544 the problem of moisture buildup and fogging is addressed by equipping the optical sample analyzing apparatus with a tray filled with a desiccant dryer material, which is meant to reduce the moisture in the internal atmosphere in the analyzing apparatus. This solution, however, is complicated and expensive as well and not service-friendly, because when the desiccant is saturated, the whole apparatus has to be disintegrated to exchange the desiccant, or one would apply a large amount of desiccant material, which makes the apparatus voluminous and expensive.